Audemars Piguet, the Swiss maker of the rugged Royal Oak watch, plans to open standalone stores to buy and sell secondhand timepieces, seeking more control over its products throughout their life cycle as the industry looks for new sources of growth.

The preowned business could be 10 to 20 times the size of the market for new watches, Chief Executive Officer Francois-Henry Bennahmias said at a show in Geneva. Until now it’s mostly been left to auction houses, independent local shops and online platforms like Amazon.com Inc. and eBay Inc., with Swiss brands focusing on building an aura of exclusivity around their new creations.

“We have to recapture that market, because we believe we can do that better,” he said in an interview at the Salon International de la Haute Horlogerie.

Switzerland’s four-century-old watchmaking industry is experimenting with new strategies after a multiyear slump that came amid a crackdown on corruption in China and the rise of the smartwatch. Last year’s export growth of about 3 percent was a far shot from the double-digit pace of the previous decade.

Audemars Piguet, which makes around 40,000 new timepieces annually and is one of an increasingly rare breed of large independent watchmakers in an industry dominated by Richemont, Swatch Group AG and Rolex, will open stores selling used models of its own brand within three years, Bennahmias said. The brand has tested the concept at a store in Geneva’s Grand Hotel Kempinski, and it plans to start trials in the U.S. and Japan.

It’s not the only brand looking into the secondhand business. Jean-Claude Biver, head of LVMH watch brands TAG Heuer, Hublot and Zenith, has said he’s considering entering the market.

One of the biggest diamonds in history has been discovered in the mountainous kingdom of Lesotho in southern Africa.

Gem Diamonds Ltd. found the 910-carat stone, about the size of two golf balls, at its Letseng mine in the country. It’s a D color Type IIa diamond, which means it has very few or no nitrogen atoms and is one of the most expensive stones. The diamond is the fifth-biggest ever found.

The Letseng mine is famous for the size and quality of the diamonds it produces and has the highest average selling price in the world. Gem sold a 357-carat stone for $19.3 million in 2015 and in 2006 found the 603-carat Lesotho Promise.

“This exceptional top-quality diamond is the largest to be mined to date and highlights the unsurpassed quality of the Letseng mine,” Chief Executive Officer Clifford Elphick said in a statement

Gem’s mega discovery follows news last week that it had found 117-carat and 110-carat stones.The biggest diamond discovered is the 3,106-carat Cullinan, found near Pretoria, in South Africa, in 1905. It was cut to form the Great Star of Africa and the Lesser Star of Africa, which are set in the Crown Jewels of Britain. Lucara’s 1,109-carat Lesedi La Rona is the second-biggest, with the 995-carat Excelsior and 969-carat Star of Sierra Leone the third- and fourth-largest.